California Governor Jerry Brown said around 10,000 people had been evacuated in the areas surrounding the Mendocino Complex fire, which has destroyed 100 structures and threatens approximately 10,000 more.

State authorities responded by saying California's water supply was not "diverted" anywhere.

In addition, Cal Fire has been engaged in a clearance operation since the fires began to halt their advance; one of the fatalities recorded was a bulldozer operator engaged in clearing operations when his bulldozer slipped.

Trump declared the California bushfires a major disaster, which allows the state and those affected to access federal funds.

Three specialist firefighters from South Australia's Country Fire Service are being deployed to Canada where authorities are battling more than 450 fires in the British Colombia district.

SA CFS assistant chief officer Daniel Austin said the service was pleased to help an international partner in a time of crisis.

"Fires do not know boundaries or borders and as a firefighting service we are ready to respond both within Australia and overseas," he said.